Another Coffee Sir?

I think I drink quite a lot of coffee a day...probably 4 cups during the day (mostly cold!) when I'm at the shop, plus others. Many pharmacists drink considerably more than this...and some people I know drink it all the time - especially when working long hours.
It started me thinking about the health benefits and risks of coffee...

Coffee is one of the most popular liquids in the world - which makes caffeine (a major component) one of the most widely consumed pharmacologically active compounds on the planet - as it is the major "active" molecule in coffee. Interestingly, however, coffee contains many thousands of other compounds, and so the effects of coffee on the body are not entirely due to the caffeine. Also, caffeine is found in tea, cola and cocoa not just coffee! The most common coffee varieties, Arabica and Robusta, contain about 100mg and 200mg respectively per average 150ml cup. Tea, cola and cocoa contain a lot less caffeine, approximately 37mg, 25mg and 4mg for a similar volume respectively.

 Most people drink coffee because they like it, although some do so because caffeine stimulates the central nervous system, alleviating fatigue, increasing wakefulness, and improving concentration and focus. 

The rate of elimination of caffeine varies between individuals, but the half life is generally between 5 and 7 hours - and this can vary between individuals by a factor of up to 4 - and also seems to be dose dependent - so it's best avoided in the evening. So no coffee after 6pm!

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So, how much coffee is ok to drink?
The most common safe level seems to be 2-4 cups of regular brewed coffee per day; and it's only when larger quantities are drunk that people experience side-effects such as: Insomnia, nervousness, restlessness, irritability etc. Some people are really sensitive to caffeine, and even low doses in people that don't drink coffee regularly can have unpleasant effects...(as some tolerance seems to develop with regular use).  Having looked into it, I guess my 4 cups of coffee are not too bad after all...I certainly don't have any of the side-effects...